SChannel in Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8, Windows 8.1, Windows Server 2012 Gol…

published 2015-11-11 10y ago modified 2026-06-17 4mo ago also EUVD-2015-6055

cvss: 5.8; version 2.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 2.8%; EPSS 2.8% chance of exploitation in 30 days, percentile 86%
public exploits: 0; none known

SChannel in Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT Gold and 8.1 lacks the required extended master-secret binding support to ensure that a server's X.509 certificate is the same during renegotiation as it was before renegotiation, which allows man-in-the-middle attackers to obtain sensitive information or modify TLS session data via a "triple handshake attack," aka "Schannel TLS Triple Handshake Vulnerability."

Patch / fix

links 1

docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-121 advisory

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Exploit prediction

2.80% chance of exploitation in the next 30 days, higher than 86% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	2.0	5.8	AV:N/AC:M/Au:N/C:P/I:P/A:N

Classification

Weakness

CWE-20 Improper Input Validation
CWE-310 Cryptographic Issues

References

docs.microsoft.com /en-us/security-updates/securitybulletins/2015/ms15-121
vendor-advisory, patch
securitytracker.com /id/1034124
vdb-entry, third-party-advisory

Sources

CVE List CVE-2015-6112
NVD CVE-2015-6112

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.